Fix FastEndpoints/Swagger wiring and missing required fields in DTOs

- Register FastEndpoints, SwaggerDocument, DbContext in Program.cs
- Add DbContextOptions constructor to PyroFetesDbContext
- Add CityId to Show DTOs and endpoints (NOT NULL in DB)
- Add F4T2NumberApproval/F4T2ExpirationDate to Staff DTOs and endpoints
- Simplify DeleteShow to rely on DB cascade instead of manual includes
- Default NOT NULL string fields to empty string on create

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

PyroFetes/Endpoints/Staff/GetStaffEndpoint.cs

@@ -23,7 +23,9 @@ public class GetStaffEndpoint(PyroFetesDbContext pf3DbContext) : Endpoint<IdStaf
                 FirstName = s.FirstName,
                 LastName = s.LastName,
                 Profession = s.Profession,
-                Email = s.Email
+                Email = s.Email,
+                F4T2NumberApproval = s.F4T2NumberApproval,
+                F4T2ExpirationDate = s.F4T2ExpirationDate
             })
             .FirstOrDefaultAsync(ct);